While the present invention is of general bonding utility, it will be described in the environment of two specific arts, namely bonding which produces magnetic or electrical isolation, without limitation thereto.
The data density which can be placed onto magnetic recording media is limited by a number of physical parameters, one of which is the gap-width of the nonmagnetic gap of the transducing head which is to write and/or read the media's data track. Gap width is measured in the direction of relative movement between the head and the magnetic recording media being transduced by the head. A great deal of prior art effort has been expended in attempts to produce thin, uniform and durable head gaps. The following are exemplary, and are incorporated herein by reference for the purpose of illustrating the state of the art and the background of the present invention.
The concept of using heat/pressure bonding methods to glass-bond adjoining layers to form the transducing gap of a magnetic head, is well known, and U.S. Pat. No. 4,182,643 is exemplary.
The use of alumina films to support the brittle ferrite material of a magnetic head, so that chipping and erosion do not occur during operation of the head slider, is taught by U.S. Pat. No. 4,298,899. In this patent, the alumina films are sputter deposited on two ceramic members. The alumina films are then bonded with a low temperature glass by diffusion or with an epoxy, thereby joining the ceramic members.
The use of colloids or slurries to deposit a layer, such as glass, on an article is known. U.S. Pat. No. 4,039,702 recognizes prior art where thin, uniform glass coatings are formed on semiconductor or electronic articles of manufacture by a variety of means, e.g. sputtering, evaporation or condensation (silox process). This patent seeks to improve a glass coating method which produces sedimentation from a fluid suspension of glass particles by means of centrifugal force; and more particularly the improvement is achieved by adding a polar substance such as hydrochloric acid, ammonium hydroxide or hydrogen peroxide to the fluid suspension. While the preferred means to coat the article is by centrifugal force, any means well known to the art whereby suspended particles may be caused to agglomerate, and thereby settle, is said to be within this patent's teaching.
The IBM TECHNICAL DISCLOSURE BULLETIN of June 1978, at page 328, describes how a very thin, uniform layer of titanium dioxide or alumina may be formed on the surface of a substrate, for the purpose of providing the surface with a diffusely reflecting medium, useful when analyzing the surface using holographic interferometry. More specifically, the surface is first cleaned, followed by dipping into an aqueous silica bath to provide a hydrophilic surface. Excess silica is washed off with water, and the surface is dried. The surface is then placed in a water-soluble inorganic polymer, followed by dipping into a slurry of titanium dioxide or alumina. Excess particles are removed by water washing, followed by air drying.
The IBM TECHNICAL DISCLOSURE BULLETIN of December 1973, at page 2369, also describes a method of depositing monolayers on a substrate, for example, in the making of magnetic media.